Tversky and Kahneman (1974)

Uses: Duel processing model, anchoring bias, heuristics

Aim: to test the influence of the anchoring bias on decision-making (An anchor is the first piece of information offered to someone who is asked to solve a problem or make a decision

IV:  Whether the anchor was a low or a high number

ASCENDING CONDITION: One condition was asked to estimate the product 1 X 2 X 3 X 4 X 5 X 6 X 7 X DECSENDING CONDITION: Participants in the other condition were asked to quickly estimate the value of 8 X 7 X 6 X 5 X 4 X 3 X 2 X 1.

DV: The estimated product

Participants: High school students

Research Method: Lab Experiment

Procedure:

In this study, high school students were used as participants.  Participants in the “ascending condition” were asked to quickly estimate the value of 1 X 2 X 3 X 4 X 5 X 6 X 7 X 8 in five seconds.

Those in the “descending condition” were asked to quickly estimate the value of 8 X 7 X 6 X 5 X 4 X 3 X 2 X 1.

Since we read from left to right, the researchers assumed that group 1 would use "1" as an anchor and predict a lower value that the group that started with "8" as the anchor.  The expectation was that the first number seen would bias the estimate of the value by the participant.

Results:

The researchers found that the median for the ascending group was 512; the median for the descending group was 2250. The actual value is 40320.

The first number seen by the participants seems to have biased the final estimate. Since they had no time to calculate in 5 seconds, they had to make an estimation based on the first few multiplications. When those numbers where smaller, the estimate was smaller.

Amos Tversky; Daniel Kahneman Science, New Series, Vol. 185, No. 4157. (Sep. 27, 1974), pp. 1124-1131. Stable URL: http://links.jstor.org/sici?sici=0036-8075%2819740927%293%3A185%3A4157%3C1124%3AJUUHAB%3E2.0.CO%3B2-M